Bitcoin Mate is a simple companion program to the official bitcoin client,it displays information on the current blockchain, and MtGox trading data and includes other bitcoin related toolsIts basically a frontend to the scripts found at https://mtgox.com/support/tradeAPI and http://blockexplorer.com/q

Its coded in C# and compiled with .NET 2.0 so it should run on any windows OS since XP sp3,Work on a cross-platform mono version as begun and it should be available soon.